High-speed print-out emulsions



United States Pater 2,888,347 HIGH-SPEED PRINT-OUT EMULSIONS Thomas R. Thompson, Joseph E. Unity, and Henry T.

Dybvig, Binghamton, N.Y., assignors to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Application May 17, 1955 Serial No. 509,111

4 Claims. (Cl. 96-94) The present invention relates to high-speed, print-out emulsions and, particularly, to such emulsions of sufiiciently high speed to enable them to be used, inter alia, in the indication of and evaluation of the quantity of ionizing radiation present in a particular area.

The development of methods leading to the fission of the atom has made it imperative that persons, subject to radioactive rays encountered with such development, be provided with means for indicating the intensity of the rays encountered. To this end, devices known as radiation monitoring badges operating with high-speed film have been devised. Such devices, however, as is evident, require that the film be processed before the ray dosage can be determined. Delays are thus encountered in arriving at an evaluation of the radioactive rays present.

It has now been discovered that these delays may be avoided by substituting for the high-speed film generally employed a photographic element bearing a high-speed, print-out emulsion permitting a dosage indication on direct inspection. Such photosensitive elements, and the preparation of the emulsions therefor, constitute the purposes and objects of the present invention.

The photosensitive elements contemplated herein are prepared by casting on a suitable base, such as paper or the like, an emulsion containing a substantial quantity of silver citrate. The silver citrate is prepared in situ in the presence of the emulsion or the components thereof.

A technique which we have found to yield the desired results involves the addition to a solution of potassium bromide and sodium chloride in gelatin of an ammoniacal solution of silver nitrate. The resulting emulsion is chilled, shredded and washed to remove excess water soluble salts. It is then remelted and there is added to this melt an aqueous solution of citric acid and silver nitrate. This mixture is maintained at about 32 C. and then coated within a period of say about 1% hours. It is found that with such an emulsion, the silver citrate operates to permit development of an image without resorting to the usual developing agents.

The following example will further illustrate the invention, although it is to be understood that the invention is not to be restricted thereto.

Water to make 37.5 cc.

Part II is added to Part I at C. After a period of 20 minutes, the mixture is chilled, shredded and washed for 30 minutes.

The product thus obtained is remelted and there is then added to 313 grams of the above product the following solutions in the indicated order:

(1) 6.25 grams of citric acid dissolved in water to make 20 cc.;

(2) 25 cc. of silver nitrate (50%).

The resulting mixture is held at 32 C. with no agitation and, after a period of say 1% hours, is coated on a base such as paper.

Such an emulsion, when utilized in lieu of the highspeed film presently employed in monitoring badges, permits a direct reading of the intensity of the rays impinging on the photosensitive element.

We claim:

1. A process of making a high-speed, print-out emulsion which comprises precipitating silver chloride and silver bromide by reaction in gelatin of silver nitrate with potassium bromide and sodium chloride chilling the reaction mixture to cause it to jell, washing to remove excess water soluble salts remelting the emulsion and adding thereto an aqueous solution of citric acid and silver nitrate to precipitate silver citrate throughout the emulsion.

2. The process as defined in claim 1, wherein the reaction designed to precipitate the silver halide is effected with an ammoniacal solution of silver nitrate.

3. A high-speed, print-out film comprising a base carrying an emulsion prepared as in claim 1.

4. A high-speed, print-out film comprising a base carrying an emulsion prepared as in claim 2.

References Cited in the tile of this patent UNITED STATES PATENTS 50,544 Smith Oct. 17, 1865 240,262 Lutz Apr. 19, 1881 FOREIGN PATENTS 471,366 Great Britain Sept. 2, 1937 

1. A PROCESS OF MAKING A HIGH-SPEED, PINT-OUT EMULSION WHICH COMPRISES PRECIPITATING SILVER CHLORIDE AND SILVER BROMIDE BY REACTION IN GELATIN OF SILVER NITRATE WITH POTASSIUM BROMIDE AND SODIUM CHLORIDE CHILLING THE REACTION MIXTURE TO CAUSE IT TO JELL, WASHING TO REMOVE AXCESS WATER SOLUBLE SALTS, REMELTING THE EMULSION AND ADDING THERETO AN AQUEOUS SOLUTION OF CRITIC ACID AND SILVER NITRATE TO PRECIPITATE SILVER CITRATE THROUGHOUT THE EMULSION. 